A typical linear aromatic polycarbonate displays nearly newtonian melt rheology, unexceptional flame resistance compared to branched polycarbonate and poor solvent resistance (i.e., complete miscibility in methylene chloride). Non-newtonian melt rheology of polycarbonates, which is advantageous for forming articles by blow molding and profile extrusion, typically has been achieved by branching the aromatic polycarbonate. Polycarbonate having improved flame resistance has typically been made using brominated monomers or by additions of known flame retardants such as antimony oxide, inorganic and organic salts of alkali and alkali earth metals. These modified polycarbonates often exhibit reduced thermal stability and increased corrosivity which leads to poor color and black specks during molding.
Polycarbonate made by a method purporting to terminate a polycarbonate with sulfonated aromatic end-caps has been described. The described polycarbonate displayed a slight non-newtonian melt rheology (U.S. Pat. No. 4,469,860). In the polycarbonate preparation method of the '860 patent, a basic aqueous interfacial polymerization process employing a sulfonated phenol or napthol terminating agent such as 4-hydroxybenzenesulfonic acid is used.
Using the process described by the '860 patent, Degee et al., Polymer, 35, (2), pp. 371-376, attempted to form a sulfonated aromatic endcapped polycarbonate by an aqueous interfacial polymerization process using 4-hydroxybenzenesulfonic acid. Degee et al. determined that no termination resulted in the process which was explained as being due to the instability of the sulfonated carbonate endcap in the presence of aqueous base resulting in a polycarbonate product which is terminated by a phenoxide moiety and not a sulfonic acid or sulfonate salt moiety.
Therefore, it would be desirable to provide a linear aromatic polycarbonate having improved flame resistance, improved solvent resistance and significant non-newtonian melt rheology and a process to form said aromatic polycarbonate.